uint8_t mcp79410_read_sram(uint8_t offset) {
uint8_t data[1];
data[0] = 0x20 + offset;
twi_write_to(0x6f, data, 1, TWI_BLOCK, TWI_NO_STOP);
twi_read_from(0x6f, data, 1, TWI_STOP);
return data[0];
}
void mcp79410_set(struct mcp79410_time_t *time) {
// see the note in section 5.3 about how to set the timekeeping registers without rollover issues
uint8_t data[7];
// disable the crystal input (ST = 0)
data[0] = 0x00; // seconds register
data[1] = 0x00; // ST = 0
twi_write_to(0x6f, data, 2, TWI_BLOCK, TWI_STOP);
// wait for the oscilator to stop (OSCRUN == 0)
data[0] = 0x03;
data[1] = 0x20;
while (data[1] & 0x20) {
twi_read_from(0x6f, data, 2, TWI_STOP);
}
// set the time fields
data[0] = 0x01; // minutes register
data[1] = hex2bcd(time->minute);
data[2] = hex2bcd(time->hour);
data[3] = hex2bcd(time->wday) | 0x08, // enable battery (VBATEN = 1)
data[4] = hex2bcd(time->mday),
data[5] = hex2bcd(time->month), // bit 5 is LPYR
data[6] = hex2bcd(time->year - 2000);
twi_write_to(0x6f, data, 7, TWI_BLOCK, TWI_STOP);
// set the seconds field and enable the crystal input (ST = 1)
data[0] = 0x00; // seconds register
data[1] = hex2bcd(time->second) | 0x80;
twi_write_to(0x6f, data, 2, TWI_BLOCK, TWI_STOP);
}
void mcp79410_get(struct mcp79410_time_t *time) {
// register, unused...
// seconds, minutes, hours, dow, date, month, year
uint8_t data[8] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
twi_write_to(0x6f, data, 1, TWI_BLOCK, TWI_NO_STOP);
twi_read_from(0x6f, data, 7, TWI_STOP);
// it's not clear from the datasheet if the unused bits are 0 or undefined
time->second = bcd2hex(data[0] & 0x7f); // bit 7 is the ST flag
time->minute = bcd2hex(data[1]);
time->hour = bcd2hex(data[2]);
time->wday = bcd2hex(data[3] & 0x07); // bit 5 is OSCRUN, bit 4 is PWRFAIL, bit 3 is VBATEN
time->mday = bcd2hex(data[4]);
time->month = bcd2hex(data[5] & 0x1f); // bit 5 is LPYR
time->year = 2000 + bcd2hex(data[6]);
}
void ds1307_get(struct ds1307_time_t *time) {
// register, unused...
// seconds, minutes, hours, dow, date, month, year
uint8_t data[8] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
twi_write_to(0x68, data, 1, TWI_BLOCK, TWI_NO_STOP);
twi_read_from(0x68, data, 7, TWI_STOP);
// it's not clear from the datasheet if the unused bits are 0 or undefined
time->second = bcd2hex(data[1] & 0x7f); // bit 7 is the CH flag
time->minute = bcd2hex(data[2]);
time->hour = bcd2hex(data[3]);
time->wday = data[4];
time->mday = bcd2hex(data[5]);
time->month = bcd2hex(data[6]);
time->year = 2000 + bcd2hex(data[7]);
}
